At present, there are many different types of downlight devices on the market. The downlight devices basically meet users' requirements, but there are still some deficiencies. Most downlight devices have lamp caps connected to light bodies through terminals, thus the heat dissipation of downlight devices is unsatisfactory. As downlight devices usually need to continuously work for a long time, the temperature of light bodies increases, which can shorten the life of downlight devices. Because of a large number of downlight components, the production process and method of installation are complicated, and the production costs increase.